1. Field of the Invention
The present invention relates to electrical power monitors and more specifically to monitors for detecting phase imbalances in a multiphase electrical system.
2. Description of the Prior Art
Monitors for detecting unbalanced or missing phase voltages in multiphase electrical power transmission systems are known in the art.
Typically, these prior art devices monitor each phase independently. The ac voltage for each phase is either averaged or peak-detected and then divided down to a level suitable for application to a solid state logic circuit usually including an AND circuit that will respond to a missing or abnormal phase voltage, and an indicating means responsive to the output of the AND circuit.
Since such prior art devices require that each phase be monitored separately, such prior art devices must include individual means to average or peak-detect each phase and individual means to reduce each phase voltage to a level suitable for processing in the logic and indicating circuits. Furthermore such prior art circuits require considerable modification if the device is to be used in conjunction with systems having a different number of phases or a different voltage level than the system for which the monitor was originally designed.
As opposed to such prior art devices the device of the present invention requires relatively few components, draws a minimum of power during normal operation, and can be readily adjusted to monitor conditions in multiphase systems of substantially any voltage or number of phases.